JP6174190B2 - Image forming apparatus, image output program, and image output method - Google Patents

Description

  The present invention relates to an image forming apparatus for adding a halftone dot to a halftone dot image, an image output program, and an image output method.

  2. Description of the Related Art Conventionally, screening using a screen such as a halftone screen or a line screen is known that converts an image into a halftone dot image composed of a periodic arrangement of halftone dots represented by gradation. In order to perform appropriate screening, various parameters such as the mesh shape (screen pattern), screen line width, and screen angle are set according to the attributes of the image before conversion. .

  When screening is performed on lightly-concentrated characters and fine lines, the distance between the halftone dots is widened, resulting in a portion where no halftone dots are arranged in the halftone dot image at the edges of the characters and fine lines. It may appear that white lines or discontinuities occur in the thin lines.

  Therefore, conventionally, there is known a method of detecting the edge portion of a character or line, selecting one of a plurality of threshold matrices having different growth methods according to the character or line attribute, and outputting the selected one. (For example, refer to Patent Document 1).

JP 2013-009124 A

  However, in the conventional method, since it is necessary to prepare a plurality of threshold matrixes, there is a problem that a large storage capacity is required for the threshold matrixes.

  Therefore, the present invention provides an image forming apparatus, an image output program, and an image output method capable of suppressing the occurrence of white spots and breaks in the edge portion of an image even when there is little information to be stored in advance. With the goal.

  An image forming apparatus according to the present invention is a halftone dot adding device for adding a halftone dot to a halftone dot image, the Voronoi diagram having a generating point corresponding to the halftone dot of the halftone dot image, centering on the Voronoi point An empty circle information acquisition unit that acquires a radius of an empty circle that passes through the generating point and does not include the generating point inside, and an object circle that is the empty circle of the target acquired by the empty circle information acquiring unit Halftone dot adding means for adding the halftone dot corresponding to the new mother point to the halftone image by adding the new mother point inside the target circle when the radius is larger than a specific value; It is characterized by providing.

  With this configuration, the image forming apparatus according to the present invention allows the object circle when the radius of the object circle, which is the object empty circle, is larger than a specific value in the Voronoi diagram including the generating point corresponding to the halftone dot of the halftone image. Since a halftone dot corresponding to the new mother point is added to the halftone image by adding a new mother point inside the circle, even if there is little information to be stored in advance, the white area at the edge of the image Occurrence of disconnection and interruption can be suppressed.

  In the image forming apparatus according to the aspect of the invention, the halftone dot adding unit may include a position of the center of the target circle and the empty circle that passes through only the two mother points with respect to the mother point through which the target circle passes. The position of the new generating point may be determined based on the position of the center of the circle.

  With this configuration, the image forming apparatus according to the present invention is newly based on the position of the center of the target circle and the position of the center of the adjacent circle that is an empty circle that passes through only two generating points for the generating point that the target circle passes. Therefore, a new halftone dot can be added at an appropriate position according to the positions of the surrounding halftone dots.

  In the image forming apparatus according to the aspect of the invention, the halftone dot adding unit may determine the position of the new base point based on the center position of the target circle and the center positions of the two adjacent circles. Also good.

  With this configuration, the image forming apparatus of the present invention determines the position of a new base point based on the position of the center of the target circle and the positions of the centers of two adjacent circles. A new halftone dot can be added at a more appropriate position.

  In the image forming apparatus of the present invention, the halftone dot adding unit may determine the position of the new base point based on the radius of the target circle and the radius of the adjacent circle.

  With this configuration, the image forming apparatus according to the present invention has a new base point based on not only the center position of the target circle and the center position of the adjacent circle but also the radius of the target circle and the radius of the adjacent circle. Therefore, a new halftone dot can be added at a more appropriate position according to the positions of the surrounding halftone dots.

  An image output program according to the present invention is a halftone dot addition program for adding a halftone dot to a halftone dot image, the Voronoi point being a center in a Voronoi diagram having a generating point corresponding to the halftone dot of the halftone dot image. An empty circle information acquisition unit that acquires a radius of an empty circle that is a circle that passes through the generating point and does not include the generating point inside, and an object circle that is the empty circle of the object acquired by the empty circle information acquisition unit As a halftone dot adding means for adding the halftone dot corresponding to the new mother point to the halftone image by adding the new mother point inside the target circle when the radius of is larger than a specific value It is characterized by functioning a computer.

  With this configuration, the image output program of the present invention allows the target circle when the radius of the target circle, which is the target empty circle, is larger than a specific value in the Voronoi diagram including the generating points corresponding to the halftone dots of the halftone image. Since a halftone dot corresponding to the new mother point is added to the halftone image by adding a new mother point inside the circle, even if there is little information to be stored in advance, the white area at the edge of the image Occurrence of disconnection and interruption can be suppressed.

  The image output method of the present invention is a halftone dot adding method for adding a halftone dot to a halftone dot image, the Voronoi diagram having a generating point corresponding to the halftone dot of the halftone dot image, centering on the Voronoi point An empty circle information acquisition step of acquiring a radius of an empty circle that is a circle that passes through the generating point and does not include the generating point inside, and an object circle that is the empty circle of the object acquired by the empty circle information acquiring step A halftone dot adding step of adding the halftone dot corresponding to the new mother point to the halftone dot image by adding the new mother point inside the target circle when the radius is larger than a specific value; It is characterized by providing.

  With this configuration, the image output method of the present invention enables the target object when the radius of the target circle, which is a target empty circle, is larger than a specific value in the Voronoi diagram including the generating points corresponding to the halftone dots of the halftone image. Since a halftone dot corresponding to the new mother point is added to the halftone image by adding a new mother point inside the circle, even if there is little information to be stored in advance, the white area at the edge of the image Occurrence of disconnection and interruption can be suppressed.

  The image forming apparatus, the image output program, and the image output method of the present invention can suppress the occurrence of white spots or breaks in the edge portion of the image even if the information stored in advance is small.

1 is a block diagram showing a configuration of an MFP according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a Voronoi diagram generated by the MFP illustrated in FIG. 1. 2 is a flowchart of the operation of the MFP shown in FIG. 1 when outputting an image based on image data. (A) is a figure which shows an example of the image based on the image data handled by the control part shown in FIG. (B) is a figure which shows an example of the halftone image produced | generated from the image shown to Fig.4 (a). 4 is a flowchart of halftone dot adjustment processing shown in FIG. 3. It is a figure which shows an example of the empty circle treated in the halftone dot adjustment process shown in FIG. 6 is a flowchart of halftone dot addition processing shown in FIG. 5. It is a figure which shows an example of the temporary Voronoi point handled in the halftone dot addition process shown in FIG. It is a figure which shows an example of the temporary mother point handled in the halftone dot addition process shown in FIG. It is a figure which shows an example of the generating point which shows the center of the additional halftone dot handled in the halftone dot addition process shown in FIG. FIG. 5 is a diagram showing a state in which halftone dots are added to the halftone image shown in FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  First, the configuration of an MFP (Multifunction Peripheral) as an image forming apparatus according to the present embodiment will be described.

  FIG. 1 is a block diagram showing a configuration of MFP 10 according to the present embodiment.

  As shown in FIG. 1, the MFP 10 is a display device such as an operation unit 11 that is an input device such as buttons for inputting various operations by a user and an LCD (Liquid Crystal Display) that displays various information. A display unit 12, a scanner 13 that is a reading device that reads an image from a document, a printer 14 that is a printing device that performs printing on a recording medium such as paper, an external facsimile apparatus (not shown), a public telephone line, and the like A fax communication unit 15 that is a fax device that performs fax communication via a communication line, a network communication unit 16 that is a network communication device that communicates with an external device via a network such as a LAN (Local Area Network), the Internet, and an EEPROM (E ectrically Erasable Programmable Read Only Memory), an HDD (Hard Disk Drive) storage unit 17 is a storage device such as, and a control unit 18 which controls the entire MFP 10.

  The storage unit 17 stores a halftone dot addition program 17 a as an image output program executed by the control unit 18. The halftone dot addition program 17a may be installed in the MFP 10 at the manufacturing stage of the MFP 10, or may be additionally installed in the MFP 10 from a storage medium such as an SD card or a USB (Universal Serial Bus) memory. To the MFP 10 may be additionally installed.

  The control unit 18 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory) storing programs and various data, and a RAM (Random Access Memory) used as a work area of the CPU. Yes. The CPU executes a program stored in the ROM or the storage unit 17.

  The control unit 18 executes a halftone dot addition program 17a stored in the storage unit 17, thereby obtaining a blank circle information obtaining unit 18a for obtaining a radius of a blank circle, which will be described later in the Voronoi diagram, and a halftone dot image. It functions as halftone dot adding means 18b for adding points.

The Voronoi diagram is a diagram in which a space closest to each generating point existing in the space is divided by a hyperplane such as a line or a surface. That is, the Voronoi diagram is the Voronoi region {V (p ₁ ), V (p ₂ ), ..., V for a finite subset P = {p ₁ , p ₂ , ..., p _n } in the metric space. It can be defined as a set of (p _n )}. Here, the Voronoi region is a region V (p _i ) configured by the following equation 1 with respect to the distance function d. In the equation shown in Equation 1, d (p, p _i ) is the distance between point p and point p _i, and d (p, p _j ) is the distance between point p and point p _j. It is.

  An empty circle is a circle that does not include a generating point inside. Here, the property of the Voronoi diagram is that a Voronoi point exists at a position equidistant from a plurality of generating points close to each other. Therefore, there is an empty circle that passes through a plurality of generating points around the Voronoi point.

  FIG. 2 is a diagram illustrating an example of the Voronoi diagram 30 generated by the MFP 10.

  As shown in FIG. 2, in the Voronoi diagram 30, the center of the halftone dot of the halftone image is the generating point 31. The Voronoi regions 32 each containing the generating point 31 are delimited by Voronoi sides 33. The intersection between the Voronoi sides 33 is called a Voronoi point 34.

  Next, the operation of the MFP 10 will be described.

  When instructed to output an image based on the image data, the control unit 18 of the MFP 10 executes the halftone dot addition program 17a and operates as shown in FIG. The image data is input by, for example, reading an image from an original by the scanner 13, input by receiving an image by FAX by the fax communication unit 15, or receiving print data by the network communication unit 16. Can be entered.

  FIG. 3 is a flowchart of the operation of the MFP 10 when outputting an image based on the image data.

  As shown in FIG. 3, the control unit 18 generates a halftone image by screening from the image data (S101).

  FIG. 4A is a diagram illustrating an example of the image 21 based on the image data handled by the control unit 18. FIG. 4B is a diagram illustrating an example of a halftone image 22 generated from the image 21 illustrated in FIG.

  In S101, for example, the control unit 18 converts the image 21 shown in FIG. 4A into a halftone image 22 shown in FIG. 4B by screening. The halftone image 22 is an image constituted by a halftone dot 22a.

  As shown in FIG. 3, when the processing of S101 is completed, the control unit 18 generates a Voronoi diagram 30 with the center of the halftone dot 22a of the halftone image 22 generated in S101 as the generating point 31 (S102).

  In S102, the control unit 18 generates, for example, the Voronoi diagram 30 shown in FIG.

  As shown in FIG. 3, when the process of S102 ends, the control unit 18 executes a halftone dot adjustment process shown in FIG. 5 for adjusting the number of halftone dots 22a of the halftone image 22 generated in S101 (S103). .

  FIG. 5 is a flowchart of the halftone dot adjustment process shown in FIG.

  As shown in FIG. 5, the empty circle information acquisition unit 18 a of the control unit 18 is a circle that does not include the mother point 31 on the inner side through the three mother points 31 around the Voronoi point 34 in the Voronoi diagram 30 generated in S 102. The coordinates and radius of each center of the empty circle 35 (see FIG. 6) are acquired (S131). Here, the empty circle information acquisition unit 18 a sets the coordinates of the Voronoi point 34 at the center of the empty circle 35 as the coordinates of the center of the empty circle 35. The empty circle information acquisition unit 18 a sets the distance between the generating point 31 through which the empty circle 35 passes and the Voronoi point 34 at the center of the empty circle 35 as the radius of the empty circle 35.

  As shown in FIG. 5, when the process of S131 is completed, the halftone dot adding unit 18b of the control unit 18 sets the variable k to the initial value “1”, then executes the processes of S133 to S135, The addition of “1” that is an increment value to the variable k is repeated until the number of empty circles that is the closing price exceeds the variable k (S132). Here, the “number of empty circles” is the total number of empty circles 35 existing in the Voronoi diagram 30 generated in S102.

  The halftone dot adding means 18b sets one empty circle 35 that is not yet considered among the empty circles 35 existing in the Voronoi diagram 30 generated in S102 (S133), and then sets the target empty circle 35 (hereinafter “target”). It is determined whether or not the radius acquired in S131 of the circle "Q" is larger than a specific value set in advance (S134).

  If the halftone dot adding unit 18b determines in S134 that it is larger than the specific value, it executes the halftone dot addition process shown in FIG. 7 for adding the halftone dot 22a to the halftone dot image 22 (S135).

  FIG. 7 is a flowchart of the halftone dot addition process shown in FIG.

  As shown in FIG. 7, the halftone dot adding means 18b sets the variable i to “1” which is the initial value, and then executes the processes of S162 and S163 and then increments the variable i to “1”. Is repeated until the variable i exceeds the final value “2” (S161).

FIG. 8 is a diagram showing temporary Voronoi points X _i handled in the halftone dot addition process shown in FIG.

In FIG. 8, the target circle Q and the empty circle 35 (hereinafter referred to as “adjacent circle S _i ”) passing through only two generating points 31 are shown for the generating point 31 through which the object circle Q passes. Here, at least two adjacent circles S _i exist for one target circle Q, one of which is the adjacent circle S ₁ and the other one is the adjacent circle S ₂ . Of the generating points 31 on the adjacent circle S _i , one of the two generating points that are also generating points 31 on the target circle Q is set as a generating point P1 _i , and the other is set as a generating point P2 _i . The temporary Voronoi point X _i is on the line segment R (Q) R (S _i ) connecting the point R (Q) indicating the center of the target circle Q and the point R (S _i ) indicating the center of the adjacent circle S _i. This is a temporary Voronoi point.

As shown in FIG. 7, the halftone dot adding means 18b calculates the coordinates of the temporary Voronoi point X _i according to a specific rule (S162). Here, various rules can be adopted as the specific rule. For example, the halftone dot adding means 18b calculates the length of the line segment R (Q) X _i connecting the point R (Q) and the temporary Voronoi point X _i and the temporary Voronoi point as shown in the following equation (2). The ratio of the length of the line segment X _i R (S _i ) connecting X _i and the point R (S _i ) is based on the radius r (Q) of the target circle Q and the radius r (Si) of the adjacent circle Si. Alternatively, the coordinates of the temporary Voronoi point X _{i that} satisfies r (Q) ^1/2 : r (S _i ) ^1/2 may be calculated.

In Equation 2, X _i , R (Q), and R (S _i ) are the coordinates of the temporary Voronoi point X _i , the point R (Q), and the point R (S _i ), respectively.

The halftone dot adding means 18b determines that the ratio of the length of the line segment R (Q) X _{i to} the length of the line segment X _i R (S _i ) is the radius r (Q) of the target circle Q and the adjacent circle. The coordinates of the temporary Voronoi point X _i which becomes r (Q): r (S _i ) based on the radius r (Si) of Si may be calculated. Further, halftone addition means 18b includes a radius r (Q) of the target circle Q, the radius r (S _i) and the coordinates of the temporary Voronoi points X _i in accordance with the rules except rule based on the adjacent circle S _i It may be calculated. For example, the halftone dot adding means 18b may set the midpoint of the line segment R (Q) R (S _i ) as the temporary Voronoi point X _i .

FIG. 9 is a diagram showing temporary mother points P ′ _i handled in the halftone dot addition process shown in FIG.

In FIG. 9, the provisional empty circle Q ′ _i is a provisional empty circle centered on the provisional Voronoi point X _i for which the coordinates have been calculated in S162 and passing through the mother point P1 _i and the mother point P2 _i . The provisional generating point P ′ _i is a provisional generating point through which the provisional empty circle Q ′ _i passes, and is an intersection of the line segment R (Q) R (S _i ) and the provisional empty circle Q ′ _i. . When there are two intersections between the line segment R (Q) R (S _i ) and the provisional empty circle Q ′ _i , the one closer to the point R (Q) indicating the center of the target circle Q The mother point P ' _i .

Here, the provisional generating point P ′ _i is a point that internally divides the line segment R (Q) X _i . Therefore, the coordinates of the temporary generating point P ′ _i are expressed by the following expression (3).

In Equation 3, P ′ _i , R (Q), and X _i are the coordinates of the temporary generating point P ′ _i , the point R (Q), and the temporary Voronoi point X _i , respectively. R (Q) P ′ _i is the length of a line segment R (Q) P ′ _i connecting the point R (Q) and the temporary generating point P ′ _i .
P ′ _i X _i is the length of a line segment P ′ _i X _i connecting the temporary generating point P ′ _i and the temporary Voronoi point X _i . Here, the line segment R (Q) P ′ _i is between the line segment R (Q) X _i connecting the point R (Q) and the temporary Voronoi point X _i and the line segment P ′ _i X _i. The relationship represented by Equation 4 is established. Further, since the line segment P ′ _i X _i is the radius of the provisional empty circle Q ′ _i , the relationship expressed by the following equation 5 holds.

In Equation 4, R (Q) X _i is the length of the line segment R (Q) X _i . In Equation 5, P1 _i X _i is the length of the line segment P1 _i X _i connecting the base point P1 _i and the temporary Voronoi point X _i .

Therefore, as shown in FIG. 7, when the process of S162 is completed, the halftone dot adding unit 18b calculates the coordinates of the temporary mother point P ′ _i by the following expression (6) (S163).

FIG. 10 is a diagram showing a base point P _k indicating the center of an additional halftone dot handled in the halftone dot addition process shown in FIG.

In FIG. 10, the coordinates of the generating point P _k indicating the center of the additional halftone dot are the coordinates of the point R (Q) indicating the center of the target circle Q and the temporary generating point P ′ ₁ starting from the point R (Q). Vec (R (Q), P ' ₁ ) indicating a vector whose end point is, and vec (R (Q), P' indicating a vector whose starting point is the point R (Q) and the temporary generating point P ' _{2 2} ) and is expressed by the following equation (7).

In Equation 7, P _k is the coordinate of the generating point P _k .

As shown in FIG. 7, the halftone dot adding unit 18b calculates the coordinates of the base point P _k indicating the center of the additional halftone dot by the expression expressed by Equation 7 after the repetition of the process in S161 (see FIG. 7). S164).

  The halftone dot adding unit 18b ends the halftone dot addition process illustrated in FIG. 7 when the process of S164 is completed.

  As shown in FIG. 5, when the halftone dot adding unit 18b determines in S134 that it is not larger than the specific value, the halftone dot adding process in S135 is not executed.

  The halftone dot adding unit 18b ends the halftone dot adjustment process shown in FIG.

Therefore, for example, in the halftone image 22 shown in FIG. 4B, the halftone dot 22a is added as shown in FIG. 11 by the halftone dot 23 centered on the generating point _Pk whose coordinates are calculated in S164. . The size of the added halftone dot 22a is the same as the size of the other halftone dot 22a.

  As shown in FIG. 3, when the halftone dot adjustment process in S103 is completed, the control unit 18 outputs a halftone image 22 in which the number of halftone dots 22a is adjusted by the halftone dot adjustment process in S103 (S104). The operation shown in FIG.

  Note that the image output method is, for example, printing by the printer 14.

  As described above, when the radius of the target circle Q is larger than a specific value in the Voronoi diagram 30 (YES in S134), the MFP 10 adds a new mother point 31 to the inside of the target circle Q. Since the halftone dot 22a corresponding to the prime point 31 is added to the halftone dot image 22 (S164), even if there is little information to be stored in advance, the occurrence of white spots or breaks in the edge of the image is suppressed. Can do.

Further, since the MFP 10 determines the position of the new base point 31 based on the position of the center of the target circle Q and the position of the center of the adjacent circle S _i (S161 to S164), the position of the surrounding halftone dot 22a A new halftone dot 22a can be added at an appropriate position according to the above.

Further, the MFP 10 determines the position of the new generating point 31 based on the position of the center of the target circle Q and the positions of the centers of the two adjacent circles S _i (S161 to S164), so the surrounding halftone dot 22a It is possible to add a new halftone dot 22a at a more appropriate position according to the position.

In addition, the MFP 10 determines a new base point 31 based not only on the center position of the target circle Q and the center position of the adjacent circle S _i but also on the radius of the target circle Q and the radius of the adjacent circle S _i. Is determined (S161 to S164), a new halftone dot 22a can be added at a more appropriate position according to the position of the surrounding halftone dot 22a.

  In the present embodiment, the generating point 31 of the Voronoi diagram 30 is arranged at the center of the halftone dot 22a of the halftone dot image 22. However, if it is a position corresponding to the halftone dot 22a, other than the center of the halftone dot 22a. It may be arranged at the position.

  The image forming apparatus of the present invention is an MFP in the present embodiment, but may be an image forming apparatus other than the MFP, such as a copier or a printer.

10 MFP (image forming apparatus)
17a Halftone dot addition program (image output program)
18a Empty circle information acquisition means 18b Halftone dot addition means 21 Image 22 Halftone dot image 22a, 23 Halftone dot 30 Voronoi diagram 31, P1i, P2i Generating point 34 Voronoi point 35 Empty circle
Q Target yen
Si adjacent circle

Claims (6)

Halftone image generation means for generating a halftone image from image data;
In the Voronoi diagram comprising a generating point corresponding to the halftone dot of the halftone image generated from the image data by the halftone image generating means, the generating point is passed inward through the three generating points with a Voronoi point as a center. Empty circle information acquisition means for acquiring the radius of an empty circle that is a circle not including
When the radius of the target circle that is the empty circle of the target acquired by the empty circle information acquisition unit is larger than a specific value, the new generating point is added by adding the new generating point inside the target circle Halftone dot adding means for adding the halftone dot corresponding to the halftone dot image;
Halftone dot image output means for outputting the halftone dot image added with the halftone dot when the halftone dot is added to the halftone dot image by the halftone dot adding means. An image forming apparatus. The halftone dot adding means acquires the position of the Voronoi point as the center of the target circle from the Voronoi diagram,
The halftone dot adding means acquires the position of the Voronoi point as the center of an adjacent circle of the target circle from the Voronoi diagram,
The adjacent circle is the empty circle that passes through the three generating points, but the three generating points that the target circle passes through only the two generating points,
The halftone dot adding means includes
The position of the center of the target circle;
The image forming apparatus according to claim 1, wherein the position of the new generating point is determined based on the position of the center of the adjacent circle. The halftone dot adding means includes
The position of the center of the target circle;
The image forming apparatus according to claim 2, wherein the position of the new generating point is determined based on the positions of the centers of the two adjacent circles. The halftone dot adding means includes
A radius of the target circle;
The image forming apparatus according to claim 2, wherein the position of the new generating point is determined based on the radius of the adjacent circle. Halftone image generating means for generating a halftone image from image data;
In the Voronoi diagram comprising a generating point corresponding to the halftone dot of the halftone image generated from the image data by the halftone image generating means, the generating point is passed inward through the three generating points with a Voronoi point as a center. Empty circle information acquisition means for acquiring the radius of an empty circle that is a circle not including
When the radius of the target circle that is the empty circle of the target acquired by the empty circle information acquisition unit is larger than a specific value, the new generating point is added by adding the new generating point inside the target circle Halftone dot adding means for adding the halftone dot corresponding to the halftone dot image, and
An image which is a computer as a halftone image output means for outputting the halftone image with the halftone dot added by the halftone dot addition means when the halftone dot is added to the halftone dot image by the halftone dot addition means An image output program for causing a forming apparatus to function. An image output method executed by an image forming apparatus,
A halftone dot image generation step for generating a halftone dot image from the image data;
In the Voronoi diagram including a generating point corresponding to the halftone dot of the halftone image generated from the image data by the halftone image generating step, the generating point passes through the three generating points centering on the Voronoi point. An empty circle information acquisition step for acquiring the radius of an empty circle that is a circle not including
When the radius of the target circle that is the empty circle of the target acquired by the empty circle information acquisition step is larger than a specific value, the new generating point is added by adding the new generating point inside the target circle Adding a halftone dot corresponding to the halftone dot image to the halftone image;
A halftone image output step of outputting the halftone image with the halftone dot added by the halftone dot addition step when the halftone dot is added to the halftone dot image by the halftone dot addition step. A featured image output method.

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